Wireless device, method of operation and computer program

ABSTRACT

A wireless device has two or more radio systems and SIM channels. At least a part of the first radio system can be shut down to reduce the power consumed by the device. This occurs if the first radio system is unable to obtain suitable service for the first SIM channel and the second radio system is at least one of: (i) providing at least some service on the second SIM channel for the device, and (ii) capable of searching for service for the first radio system.

FIELD OF THE INVENTION

The present invention relates to a wireless device, a method ofoperating a wireless device and a computer program for operating awireless device.

BACKGROUND OF THE INVENTION

A multi-SIM (subscriber identity module) wireless device, includingparticularly mobile devices such as mobile phones (including so-called“smart phones”), personal digital assistants, tablet and laptopcomputers, etc., can hold two or more SIM cards. Currently, such devicescan typically hold two SIM cards, though phones that can hold three SIMcards are now available and it is likely that phones and other wirelessdevices that can hold more SIM cards will become available. It ismentioned here that there are proposals to replace SIM cards with SIMfunctionality provided by software in the device. Reference will be madein this specification generally to “SIM” to mean that part of a devicethat provides for the subscriber identity module functionality whetherprovided by a physical card, software elsewhere in the device, or anyother suitable arrangement. In addition, for simplicity and brevity,reference will often be made in this specification to a dual-SIM device,which can operate with two networks and/or tariff arrangements, etc.,but it will be understood that much of what is described herein can beapplied to a multi SIM wireless device having in principle any number ofSIMs for operating with a corresponding number of networks and/or tariffarrangements, etc.

Dual-SIM operation allows the use of two services without the need tocarry two devices at the same time. For example, the same handset can beused for business and private use with separate numbers and bills. Asanother example, the same handset can be used for travel, with one SIMbeing for use in the home country and the other SIM being for thecountry visited. As another example, both SIMs may be used with the samenetwork operator, for example to achieve a higher total bandwidth fordata connections. As yet another example, the device may contain bothcellular and non-cellular radios which are used for voice and datacommunication respectively using the different SIMs. In any event, usingmultiple SIMs allows the user to take advantage of different pricingplans for calls and text messages to certain destinations as well asmobile data usage, and/or to keep personal and business use separate forexample, and/or to achieve higher bandwidth, and/or to obtain coverageacross different networks using a single handset. With this multiple SIMfunctionality, the SIMs can in general be from any network operator. Theembodiments described herein are particularly concerned with mobilewireless devices that have two (or more) SIMs and radio systems whichcan be used simultaneously, and thus allow for example a user to send orreceive data whilst making a voice call, and/or to have plural voicecalls active simultaneously, and/or to have plural data calls activesimultaneously, all on the one device and using the separate radiosystems.

It can be expected that in practice, one of the two SIMs in theseexamples will spend a significant amount of time out of suitableservice. Suitable service is allowed service on the home network, anequivalent network or an allowed roaming network. The typical states forthe SIM in such a case are performing searches to return to suitableservice and/or camping on an acceptable network to at least provideemergency service. However, even in these states, considerable power isconsumed by the SIM channel, particularly by the receiver components(which in general will include the antenna(s), radio frequency system,processor system, etc. servicing the SIM channel for that SIM). It maybe noted here that these states are often called “idle” states eventhough the SIM channel is consuming power. A particular problem with adual (or more) SIM device is the high level of power consumed by thedevice, particularly for those that duplicate the radio hardware,software, firmware, etc.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there isprovided a method of operating a wireless device having at least a firstradio system for a first SIM channel and a second radio system for asecond SIM channel, the method comprising: determining whether a firstradio system of the wireless device is unable to obtain suitable servicefor the first SIM channel; and, shutting down at least a part of thefirst radio system to reduce the power consumed by the device if thefirst radio system is unable to obtain suitable service for the firstSIM channel and a second radio system of the wireless device is at leastone of: (i) providing at least some service on the second SIM channelfor the device, and (ii) capable of searching for service for the firstradio system.

The present invention recognises that having a radio system fullypowered and operating in a wireless device when it is unable to findsuitable service for the corresponding SIM channel can consume powerunnecessarily. This can be the case if for example the other radiosystem and SIM channel is already providing at least some service,including as a particular example emergency service (which is a legalrequirement in many countries for many wireless devices, such as mobilephones, etc. and is desirable in any event). Another example is wherethe other radio system can look for service for the first radio systemand therefore there is nothing to be gained by also having the firstradio system looking for its own service. A particular case where thismay be relevant is where the other radio system has at least an equalability to find service as the first radio. This may be when the tworadio systems use the same frequency and network protocol, etc., andperhaps are even camped on the same network cell (for example in idlemode). The radio systems can in this sense be regarded as “symmetric”.Another particular case is where the radio capabilities of the firstradio system can be regarded as a subset of those of the other radiosystem. In either case, there is nothing to be gained by having bothradio systems operating fully in the case that one of them is unable tofind suitable service because the other radio system will or can sweepthe same frequency bands, etc. that would be used by the first radiosystem. It may be noted that there will be situations, including thosejust described, where the other radio system is both capable ofsearching for service for the first radio system and providing at leastsome service (such as emergency service as a particular example) for thedevice.

In any event, the preferred embodiments of the present invention allowsignificant power savings to be made by shutting down at least part ofthe radio system supporting the out-of-service SIM. For example, searchprocedures, memory retention operations, leakage through logic gates andclocks will all consume power when the receiver is operating andpowering or shutting down at least some of these will save power.Preferably, as much of the radio system as possible is shut down and isshut down as far as possible, as discussed further below.

Suitable service is allowed service on the home network, an equivalentnetwork or an allowed roaming network. The typical states for the SIM insuch a case are performing searches to return to suitable service and/orcamping on an acceptable network to at least provide emergency service.In the context of the present specification, “shut down” will beunderstood to include any operation that reduces the power consumption,and may include for example simply shutting off clocks to a processor,

In an embodiment, the method comprises the second radio system searchingfor suitable service for the first SIM channel whilst said at least partof the first radio system is shut down. Such searching often can beaccommodated within normal operation of the second radio system withoutaffecting the normal operation of the second radio system. An example iswhen the second radio system is in an idle state (i.e. not being usedactively for a voice or data call for example).

In an embodiment, the method comprises resuming the first radio systemif the second radio system locates suitable service for the first SIMchannel. In this case, it can be useful for the second radio system todeliver information to the first radio system about the service that hasbeen found, i.e. the second radio system can deliver (or give accessfor) the required context (i.e. the frequency band and otherconfiguration and state information, etc. for the network) so that thefirst radio system does not need to search for the service itself, whichspeeds the resumption process.

In an embodiment, the method comprises resuming the first radio systemif the second radio system becomes unable to search for suitable servicefor the first SIM channel. This may be necessary if for example thesecond radio system goes to an active state, such as being used for avoice or data call.

In an embodiment, the second radio system searches periodically forsuitable service for the first SIM channel whilst said at least part ofthe first radio system is shut down, comprising using a first timeperiod between consecutive searches if it is determined that thewireless device is stationary and using a second time period betweenconsecutive searches if it is determined that the wireless device ismoving, the second time period being shorter than the first time period.This enables a further power saving as it is deemed less likely thatsuitable service will be found for the first SIM channel if the deviceis stationary rather than moving, and so searching is minimised when thedevice is stationary.

In an embodiment, the method comprises resuming the first radio systemif the second radio system becomes unable to provide emergency service.This allows the first radio system to search for at least emergencyservice, maximising the chance that it will be found. This may beparticularly the case if the radio systems are not “symmetric” as thefirst radio system will be searching on different frequencies and/ornetwork operators and/or different protocols from those used by thesecond radio system, or because different antenna arrangements are usedin the device for the two radio systems.

According to a second aspect of the present invention, there is provideda wireless device, the device comprising: at least a first radio systemfor a first SIM channel and a second radio system for a second SIMchannel; and, a processing system; the processing system being arrangedto determine whether the first radio system is unable to obtain suitableservice for the first SIM channel; and, the processing system beingarranged to shut down at least a part of the first radio system toreduce the power consumed by the device if the first radio system isunable to obtain suitable service for the first SIM channel and a secondradio system of the wireless device is at least one of: (i) providing atleast some service on the second SIM channel for the device, and (ii)capable of searching for service for the first radio system.

According to a third aspect of the present invention, there is provideda computer program comprising code such that when the computer programis executed on a computing device, the computing device is arranged to:determine whether a first radio system of a wireless device is unable toobtain suitable service for a first SIM channel; and, shut down at leasta part of the first radio system to reduce the power consumed by thedevice if the first radio system is unable to obtain suitable servicefor the first SIM channel and a second radio system of the wirelessdevice is at least one of: (i) providing at least some service on thesecond SIM channel for the device, and (ii) capable of searching forservice for the first radio system.

There is also provided a processing system for a wireless device havingat least a first radio system for a first SIM channel and a second radiosystem for a second SIM channel, the processing system being arranged tocause a said wireless device to carry to a method according as describedabove.

Further features and advantages of the invention will become apparentfrom the following description of preferred embodiments of theinvention, given by way of example only, which is made with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematically an example of a dual-SIM wireless deviceaccording to an embodiment of the present invention;

FIGS. 2A and 2B show flow diagrams of steps involved in two examples ofat least partially shutting down a radio system of the device; and

FIG. 3 shows a flow diagram of steps involved in an example of poweringup a radio system of the device.

DETAILED DESCRIPTION OF THE INVENTION

Again, for simplicity, reference will typically be made in the followingdescription to a dual-SIM wireless device (which includes particularlymobile devices, including mobile phones (including so-called “smartphones”), personal digital assistants, tablet and laptop computers,etc.), which can hold or cater for two SIMs and correspondingly has tworadio systems, one for each SIM. It will be understood however thatthese principles can be applied to a multi-SIM wireless device havingmore than two SIMs (and typically a corresponding number of radiosystems).

Referring initially to FIG. 1, a dual-SIM wireless device 10 has a radiofront end 20,30 for each of two SIMs 21,31. Each radio front end 20,30has its own respective antenna or set of antennas 22,32. Each radiofront end 20,30 receives and transmits signals for the SIM channelscorresponding to the respective SIMs 21,31 via circuitry 40 showngenerically and schematically in the diagram. In general, the radiofront ends 20,30 may provide the physical layer, baseband, MAC (mediaaccess control) and link layer control for the two SIM channels and thecircuitry 40 may host the application layers of the device 10. Otherarrangements are possible, such as the radio front ends 20,30 providingthe physical layer and baseband control and the circuitry 40 or someother common part providing MAC and link layer control. As anotheralternative, there may be a common baseband block for both radio frontends 20,30. In any event, the circuitry 40 provides a supervisory layerfor overall control of the radio front ends 20,30 and the associatedcircuitry as discussed further below. It will be understood that theradio front ends 20,30 and the circuitry 40 may in practice byimplemented by one or more silicon chips or chipsets. The control may betypically as a software implementation, though a hardware or combinationof software and hardware implementation is also possible. The term“radio system” will typically be used in this specification to refer toone or more of the radio front end, antenna(s), and relevant processingcircuitry and software for a particular SIM channel (i.e. the hardware,software and/or firmware providing service in the device 10 for aparticular SIM 21,31). In at least some circumstances, the term “radiosystem” is used to refer to all of the components for a particular SIMchannel in the device 10. The two SIMs 21,31 and their respectivechannels and associated circuitry and antennas are generally designatedby “A” and “B” in this description and the drawings.

Examples of operation of the device 10 will now be given with referenceto FIGS. 2A, 2B and 3.

Referring first to step 200 in FIG. 2A, in this embodiment, initiallythe two radio systems RADIO_A and RADIO_B are providing suitable servicefor the SIM channels corresponding to their respective SIMs SIM_A andSIM_B. “Suitable service” is allowed service on the home network, anequivalent network or an allowed roaming network.

In step 210, it is determined that RADIO_A has lost suitable service forSIM_A. This may be determined by the supervisory layer in the circuitry40 detecting or being informed that RADIO_A has lost suitable servicefor SIM_A and has not been able to regain suitable service for apredetermined period of time (which may be for example tens of secondsor perhaps a few minutes) or after a predetermined number of attempts toregain suitable service. It should be noted that even though RADIO_A haslost suitable service, at this time it may nevertheless be searching forany service and/or camped on an acceptable network cell to provideemergency service.

In step 220, the supervisory layer in the circuitry 40 notes that SIM_Band RADIO_B are providing at least emergency service (in an idle campedstate).

As a result of it being determined that RADIO_A has lost suitableservice for SIM_A in step 210 and that SIM_B and RADIO_B are providingat least emergency service in step 220, in step 230 at least part ofRADIO_A is shut down by the supervisory layer in the circuitry 40. Inaddition, in this example, the supervisory layer routes periodicsearches for SIM_A to RADIO_B so that RADIO_B takes over trying to findsuitable service for SIM_A. RADIO_B typically uses the PLMN (public landmobile network) of SIM_A as the target and operates as per the normalcellular procedures for PLMN searching. These searches are performedwhile maintaining idle camping procedures on SIM_B, including providingat least emergency service for the device 10. The time between searchescan be set to a suitable period to avoid fast battery drain. This searchperiod may also be adaptive taking into account, for example, detectionof movement by RADIO_B and/or the device 10 generally to further savepower. A shorter time period may be used if it is determined thatRADIO_B is moving and a longer time period used if RADIO_B is stationaryas in practice it less likely that suitable service will be found forthe first radio system if the device is stationary rather than moving,and so searching is minimised when the device is stationary. Inaddition, if RADIO_B is not moving, RADIO_B may sweep over a smallernumber or range of frequencies again to minimise power usage. Detectionof mobility by RADIO_B and/or the device 10 generally can be made in anumber of ways, such as by detecting a change in received signalstrength or seeing new neighbouring network cells at RADIO_B, changes infrequency owing to the Doppler effect (particularly if moving fast suchas in a moving vehicle), use of GPS signals in a GPS-equipped device,etc.

Referring now to step 250 in FIG. 2B, in this embodiment, again the tworadio systems RADIO_A and RADIO_B are initially providing suitableservice for the SIM channels corresponding to their respective SIMsSIM_A and SIM_B.

In step 260, it is determined that RADIO_A has lost suitable service forSIM_A. As above, this may be determined by the supervisory layer in thecircuitry 40 detecting or being informed that RADIO_A has lost suitableservice for SIM_A and has not been able to regain suitable service for apredetermined period of time (which may be for example tens of secondsor perhaps a few minutes) or after a predetermined number of attempts toregain suitable service. It should be noted that even though RADIO_A haslost suitable service, at this time it may nevertheless be searching forany service and/or camped on an acceptable network cell to provideemergency service.

In step 270, the supervisory layer in the circuitry 40 notes thatRADIO_B has at least an equal ability to find service as RADIO_A. Asnoted above, this may for example be on the basis that RADIO_A andRADIO_B use the same frequency and network protocol, etc., and perhapsare even camped on the same network cell (for example in idle mode), orthat the radio capabilities of RADIO_A can be regarded as a subset ofthose of RADIO_B.

In any event, as a result of it being determined that RADIO_A has lostsuitable service for SIM_A in step 260 and that RADIO_B has at least anequal ability to find service as RADIO_A as noted in step 270, in step280 at least part of RADIO_A is shut down by the supervisory layer inthe circuitry 40. In addition, in this example, the supervisory layeragain routes periodic searches for SIM_A to RADIO_B so that RADIO_Btakes over trying to find suitable service for SIM_A. These searches maybe carried out as described for the other embodiment above.

Referring now to FIG. 3, at step 300, in this example, initially RADIO_Ahas been at least partially shut down and RADIO_B is providing at leastemergency service for the device 10 and typically also providingsuitable service, and is also searching for suitable service for SIM_A.

At step 310, the supervisory layer in the circuitry 40 receives atrigger that indicates that RADIO_A should be powered up to resumeproviding service for SIM_A. A number of triggers may be used.

For example, as shown at 312, one trigger is that it is determined thatRADIO_B is unable to continue searching for a suitable service forSIM_A. This may be because RADIO_B is no longer “idle” and is forexample involved in a voice or data call (as indicated for example by achange in its RRC (radio resource control) state).

As another example, as shown at 314, a trigger may be that RADIO_B findssuitable service for SIM_A. This may be indicated in one embodiment bythe PLMN search, which is being carried out by RADIO_B on behalf ofSIM_A, returning network cells that match the desired PLMN or anequivalent PLMN. In this case, RADIO_B may deliver or at least provideaccess to the SIM context to RADIO_A as that will save time becauseRADIO_A will not have to carry out its own context acquisition process.

As yet another example, as shown at 316, a trigger may be that RADIO_Bis unable to provide emergency service. This may occur if RADIO_B isitself unable to connect to a network (perhaps after a number ofattempts, or after a predetermined period of time). In that case, it isdesirable (and in some countries a legal requirement) that RADIO_A bepowered up also to search for a network to provide at least emergencyservice, maximising the chance that it will be found (possibly becauseRADIO_A uses different frequency bands or network operator or protocol,or has a different antenna arrangement from RADIO_B). Other triggers mayalso be used.

In any event, in step 320, RADIO_A is commanded by the supervisory layerin the circuitry 40 to power up in order to resume providing service forSIM_A. Searches to find service for SIM_A are routed back to RADIO_A bythe supervisory layer in the circuitry 40 in step 330.

The preferred embodiments of the present invention provide a dual SIMdevice that at least partially shuts or powers down one of its radiosystems when that radio system is unable to find service for thecorresponding SIM and when the other SIM and its radio system is alreadyproviding at least emergency service for the device, the other radiosystem searching for suitable service for the powered-down radio system.This provides for significant power savings without affecting orcompromising normal operation of the wireless device and particularlywithout any or any significant reduction in service for the user. Theshut down radio system is powered up as necessary or desirable.

It is mentioned above that (at least part of) the radio system that isunable to obtain suitable service is shut or powered down. Power savingmethods which can be adopted will in practice depend on the specifichardware that is implemented and on certain functional criteria. Forexample, in general, processors, logic and receiver hardware can be putinto a low power state by slowing down or suspending clock signals,although logic leakage typically still continues. To reduce consumptionfurther, power domains may be implemented such that parts of the systemcan have power removed entirely. As mentioned, the device 10 may haveentirely separate hardware (such as different baseband chips and radiofront ends) for the two channels, and so one set can be fully powereddown without affecting the other. If some parts are in common, forexample the baseband logic of the two channels are on a common ASIC orother device, having different power domains for the logic or otherhardware relating to the different channels may be particularlybeneficial. Memory systems can be put into a low power retention statewhere the memory contents remain or can be shut down completely and thecontents lost. A subset of the memories may be maintained to beavailable to enable a fast resume. By combinations of reducing the powerstate on some parts and removing power on other parts, the desiredcharacteristics of reduced power consumption whilst maintaining a highresumption speed can be obtained and optimised for a particularimplementation. It will be understood that in general, adding more powerdomains complicates the power supply arrangement and is minimised wherepossible.

In general terms, for this purpose, one or more of the components makingup the radio system (such as the antenna(s), radio frequency systemhardware components, processor system hardware components, etc.) for aSIM channel can be shut or powered down to a lower power state andpreferably to the lowest power state that is available and appropriate.The “lowest power state” may be the state from which the radio systemcan be resumed in a reasonable time, particularly in the context of thethree example trigger conditions mentioned above. For example, the speedto return to suitable service may be of the order of minutes. On theother hand, the speed to gain emergency service is more urgent, thoughtens of seconds is reasonable.

Although at least some aspects of the embodiments described herein withreference to the drawings comprise computer processes performed inprocessing systems or processors, the invention also extends to computerprograms, particularly computer programs on or in a carrier, adapted forputting the invention into practice. The program may be in the form ofsource code, object code, a code intermediate source and object codesuch as in partially compiled form, or in any other form suitable foruse in the implementation of processes according to the invention. Thecarrier may be any entity or device capable of carrying the program. Forexample, the carrier may comprise a storage medium, such as a ROM, forexample a CD ROM or a semiconductor ROM, or a magnetic recording medium,for example a floppy disk or hard disk.

The above embodiments are to be understood as illustrative examples ofthe invention. Further embodiments of the invention are envisaged. Forexample, it is mentioned that in one embodiment the radio system RADIO_Aproviding suitable service performs searches for suitable service forthe powered-down radio system RADIO_B while maintaining idle campingprocedures on SIM_A, but the invention is not limited to RADIO_A beingin an idle state for this purpose. The end user may define what isregarded as “suitable service” for the device 10. For example, the enduser may configure the device 10 such that SIM_A is used only on thehome network and roaming is allowed only with SIM_B. As another example,more than two SIMs and more than two radio systems may be employed inthe device.

It is to be understood that any feature described in relation to any oneembodiment may be used alone, or in combination with other featuresdescribed, and may also be used in combination with one or more featuresof any other of the embodiments, or any combination of any other of theembodiments. Furthermore, equivalents and modifications not describedabove may also be employed without departing from the scope of theinvention, which is defined in the accompanying claims.

What is claimed is:
 1. A method of operating a wireless device having atleast a first radio system for a first subscriber identity module (SIM)channel and a second radio system for a second SIM channel, the methodcomprising: determining whether a first radio system of the wirelessdevice is unable to obtain suitable service for the first SIM channel;shutting down at least a part of the first radio system to reduce thepower consumed by the device if the first radio system is unable toobtain suitable service for the first SIM channel and a second radiosystem of the wireless device is at least one of: (i) providing at leastsome service on the second SIM channel for the device, and (ii)configured for searching for service for the first radio system;routing, within the wireless device, a search for the first SIM channelfrom the first radio system to the second radio system; in response tothe search routed from the first radio system to the second radiosystem, searching with the second radio system for suitable service forthe first SIM channel while said at least part of the first radio systemis shut down; and resuming the first radio system if the second radiosystem becomes unable to search for suitable service for the first SIMchannel.
 2. A method according to claim 1, comprising resuming the firstradio system if the second radio system locates suitable service for thefirst SIM channel.
 3. A method according to claim 1, wherein the secondradio system searches periodically for suitable service for the firstSIM channel whilst said at least part of the first radio system is shutdown, comprising using a first time period between consecutive searchesif it is determined that the wireless device is stationary and using asecond time period between consecutive searches if it is determined thatthe wireless device is moving, the second time period being shorter thanthe first time period.
 4. A method according to claim 1, wherein the atleast some service includes at least emergency service for the device.5. A method according to claim 1, comprising resuming the first radiosystem if the second radio system becomes unable to provide emergencyservice.
 6. A processing system for a wireless device having at least afirst radio system for a first subscriber identity module (SIM) channeland a second radio system for a second SIM channel, the processingsystem being arranged to cause a said wireless device to carry to amethod according to claim
 1. 7. A method according to claim 1, whereinsearching with the second radio system for suitable service for thefirst SIM channel comprises searching with the second radio system forsuitable service for the first SIM channel while the second radio systemis in an idle camped state.
 8. A method according to claim 7, furthercomprising resuming the first radio system if the second radio system isno longer in the idle camped state and is involved in a voice or datacall.
 9. A method according to claim 1, further comprising causing SIMcontext or access to SIM context to be provided to the first radiosystem in conjunction with resumption of the first radio system.
 10. Awireless device, the device comprising: at least a first radio systemfor a first subscriber identity module (SIM) channel and a second radiosystem for a second SIM channel; and, a processing system; theprocessing system being arranged to determine whether the first radiosystem is unable to obtain suitable service for the first SIM channel;the processing system being arranged to shut down at least a part of thefirst radio system to reduce the power consumed by the device if thefirst radio system is unable to obtain suitable service for the firstSIM channel and a second radio system of the wireless device is at leastone of: (i) providing at least some service on the second SIM channelfor the device, and (ii) configured for searching for service for thefirst radio system; the processing system being configured to route,within the wireless device, a search for the first SIM channel from thefirst radio system to the second radio system; and in response to thesearch routed from the first radio system to the second radio system,the processing system being further configured to cause the second radiosystem to search for suitable service for the first SIM channel whilesaid at least part of the first radio system is shut down, wherein theprocessing system is arranged to resume the first radio system if thesecond radio system becomes unable to search for suitable service forthe first SIM channel.
 11. A device according to claim 10, wherein theprocessing system is arranged to resume the first radio system if thesecond radio system locates suitable service for the first SIM channel.12. A device according to claim 10, wherein the second radio system isarranged to search periodically for suitable service for the first SIMchannel whilst said at least part of the first radio system is shutdown, the second radio system being arranged to use a first time periodbetween consecutive searches if it is determined that the wirelessdevice is stationary and to use a second time period between consecutivesearches if it is determined that the wireless device is moving, thesecond time period being shorter than the first time period.
 13. Adevice according to claim 10, wherein the at least some service includesat least emergency service for the device.
 14. A device according toclaim 10, wherein the processing system is arranged to resume the firstradio system if the second radio system becomes unable to provideemergency service.
 15. A device according to claim 10, wherein theprocessing system is configured to search with the second radio systemfor suitable service for the first SIM channel by searching with thesecond radio system for suitable service for the first SIM channel whilethe second radio system is in an idle camped state.
 16. A deviceaccording to claim 15, wherein the processing system is furtherconfigured to resume the first radio system if the second radio systemis no longer in the idle camped state and is involved in a voice or datacall.
 17. A device according to claim 10, wherein the processing systemis further configured to cause SIM context or access to SIM context tobe provided to the first radio system in conjunction with resumption ofthe first radio system.
 18. A computer program stored on anon-transitory computer readable medium comprising code such that whenthe computer program is executed on a computing device, the computingdevice is arranged to: determine whether a first radio system of awireless device is unable to obtain suitable service for a firstsubscriber identity module (SIM) channel; shut down at least a part ofthe first radio system to reduce the power consumed by the device if thefirst radio system is unable to obtain suitable service for the firstSIM channel and a second radio system of the wireless device is at leastone of: (i) providing at least some service on the second SIM channelfor the device, and (ii) configured for searching for service for thefirst radio system; route, within the wireless device, a search for thefirst SIM channel from the first radio system to the second radiosystem; and in response to the search routed from the first radio systemto the second radio system, cause the second radio system to search forsuitable service for the first SIM channel while said at least part ofthe first radio system is shut down, wherein the code is such that thefirst radio system is resumed if the second radio system becomes unableto search for suitable service for the first SIM channel.
 19. A computerprogram according to claim 18, wherein the code is such that the firstradio system is resumed if the second radio system locates suitableservice for the first SIM channel.
 20. A computer program according toclaim 18, wherein the code is such that the second radio system searchesperiodically for suitable service for the first SIM channel whilst saidat least part of the first radio system is shut down, wherein a firsttime period is used between consecutive searches if it is determinedthat the wireless device is stationary and a second time period is usedbetween consecutive searches if it is determined that the wirelessdevice is moving, the second time period being shorter than the firsttime period.
 21. A computer program according to claim 18, wherein thecode is such tha the at least some service includes at least emergencyservice for the device.
 22. A computer program according to claim 18,wherein the code is such that the first radio system is resumed if thesecond radio system becomes unable to provide emergency service.
 23. Acomputer program according to claim 18, wherein the computing device isconfigured to search with the second radio system for suitable servicefor the first SIM channel by searching with the second radio system forsuitable service for the first SIM channel while the second radio systemis in an idle camped state.
 24. A computer program according to claim23, wherein the computing device is further configured to resuming thefirst radio system if the second radio system is no linger in the idlecamped state and is involved in a voice or data call.
 25. A computerprogram according to claim 18, wherein the computing device is furtherconfigured to cause SIM context or access to SIM context to be providedto the first radio system in conjunction with resumption of the firstradio system.